Field of the Invention
This invention relates generally to a tool of the type used to service a torsion bar suspension system in a motor vehicle, and more particularly toward an unloading tool used to remove and restore spring energy in a torsion bar suspension system.
Related Art
Some motor vehicle suspensions use a torsion bar as a weight bearing spring. In this arrangement, one end of a long, usually metal torsion bar is attached firmly to the vehicle chassis and its opposite end is attached to an unsprung suspension component such as a suspension arm, spindle, axle or the like. Vertical motion of the vehicle wheel causes the torsion bar to twist which is resisted by the torsion bar's inherent spring resistance. The end of the torsion bar that is attached to the chassis is usually fitted with a crank-like or lever-like adjusting arm that is controlled by an adjusting bolt to accomplish height adjustments of the spring-weight portions of the vehicle. Over time, fatigue, wear and creep will necessitate periodic height adjustment of the torsion bar suspension system as part of routine vehicle maintenance. Likewise, a change in wheel size or the addition of a so-called “lift kit” may also necessitate adjustment of suspension height by manipulating the adjustment arm portion of the torsion bar suspension system. For this purpose, the adjusting bolt is fitted between the adjusting arm and a rigid hollow frame rail, in which the adjusting arm is stationed. Inside this hollow frame rail, the adjusting area remains relatively sheltered.
In order to service the torsion bar suspension system, which may include replacing the torsion bar or recalibrating the adjusting arm, it is usually necessary to relieve all of the stored spring energy in the torsion bar and also remove the adjusting bolt. Relieving the stored spring energy in a controlled manner can be a difficult and somewhat dangerous operation, as the torsion bar stores a tremendous amount of energy and the adjusting bolt is held in compression between the adjusting arm and the frame rail. Therefore, an unloading tool is required to temporarily transfer spring energy away from the adjusting bolt so that it can be removed or disabled before carefully releasing all of the torsion spring energy.
Current unloader tools have been proposed and are variously configured. One common type of unloader tool resembles a C-clamp which is placed over the frame rail and its screw shaft turned into engagement with the adjusting arm. By advancing the screw shaft far enough, spring energy is transferred from the adjusting bolt to the unloader tool. Once the adjusting screw has been disabled, the unloader tool can be manipulated to slowly release the stored spring energy. Other examples of prior art unloader tools may be configured differently, such as resembling a wheel or gear puller, but operate in the same general fashion.
A problem inherent with all of the prior art unloader tools resides in their tendency to slip out of position during operation. Due to the extremely large amounts of energy stored in a torsion spring, a slipping unloader tool can cause injury or damage when the stored energy is released in an uncontrolled manner. Some attempts have been made to address the slippage problem. For example, in many General Motors trucks equipped with torsion bar suspension, a small pilot hole is formed in the top of the frame rail, and a special unloader tool includes a small stem adapted to register in the pilot hole. When this style of unloader tool is hung over the rail, the stem on the unloader tool seats in the pilot hole in the frame rail, thus helping to keep it in position during the unloading process. However, this stem prevents the GM-style unloader tool from being used to work on suspension systems which are not equipped with a hole in the frame rail. Therefore, this type of prior art unloader tool is not at all versatile and therefore it is not attractive to service operators that repair various makes and styles of torsion suspension systems.
Furthermore, prior art unloader tools are susceptible to twisting out of position or into disadvantageous positions as the screw shaft is tightened against the adjusting arm or as attempts are made to carefully release the stored energy. As stated earlier, there is extremely large amounts of energy stored in the torsion spring, and therefore large amounts of force are required to displace the adjusting arm sufficiently far enough to disable and re-enable the adjusting bolt during the various phases of a service operation. This large force creates a high degree of friction at the point of contact between the tip of the screw shaft and the adjusting arm. This friction can cause the unloader tool to undesirably twist or shift out of position, increasing the chances for the tool slipping out of place and causing injury or damage. To counteract this undesirable twisting, a service operator may be tempted to use a free hand to hold the unloader tool in position. However, this increases the chances for injury. It is, in fact, not desirable for an operator's fingers to be placed on or near the unloader tool as a safety measure in the event the tool slips out of position. Again, because of the very large amounts of force and energy involved, substantial injury may result if the tool slips out of position while an operator's fingers are in close vicinity.
Accordingly, there is a need in this field to provide an unloading tool, and an improved method for safely unloading and reloading torsion spring systems, which is versatile among all motor vehicle makes and types, which is convenient to use, which is easy to manufacture and distribute, and which reduces the risk of injury to an operator.